The design of a housing for a typical desktop personal computer or workstation is, in part, constrained by the size and heat transfer requirements of the components contained in the housing. These components typically include electronic components mounted on printed circuit boards, one or more disk drives, and a power supply.
The heat generated by the power supply and other internal components must be removed to prevent overheating and resultant damage to those components. Also, heat generated by certain components, particularly the power supply, must be isolated from the other internal components, which are often temperature sensitive.
Prior art desk top computers typically include rectangular housings made of sheet metal or plastic. A typical prior art cooling system design for such a housing is shown in FIG. 1. The power supply 120 is typically mounted adjacent to the back wall 125 of the housing. A fan 130 is mounted in a vertical position immediately in front of or in back of the power supply. The housing shown in FIG. 1 also includes a floppy disk drive module 140, a hard disk drive module 145, and a main printed circuit board 150. A series of vent openings 135 are formed in the housing to receive an influx of ambient air. As shown by the arrows in FIG. 1, the vent openings are typically distributed along the front, back and sides of the housing to provide for sufficient distribution of cooling air to the internal components. Air enters the housing through vent openings 135, is drawn by fan 130 through the housing and through power supply 120, and is finally exhausted through an outlet 155 at the back of the housing.
Power supply 120 of the prior art cooling system shown in FIG. 1 is cooled by air circulated by the fan 130 through the power supply's housing 160. Heat is transferred from the power supply to the cooling air inside of the housing itself. The surface area of the available heat transfer surfaces is limited by the housing's physical size. In desktop computer designs, housings of relatively small size and volume are preferred to accommodate a small desk area. In general, the degree of cooling that can be achieved by electronic component housing cooling systems is dependent on the volume and velocity of the air flowing over the heat transfer surfaces of the devices being cooled and by the surface area of those heat transfer surfaces. To provide an adequate amount of cooling, therefore, given the limited size of the power supply housing 160, a relatively large volume of cooling air is required.
The volume of the available airflow is dependent on the volumetric flow rate of the cooling fans used. This, in turn, is dependent on the size and speed of the cooling fans. A given volume of airflow can be achieved by a small, high speed fan or, equivalently, by a large, slow speed fan. As the speed of the fan increases, so does the level of noise and vibration caused by the fan. For a vertically mounted fan, such as is typical in the prior art, the maximum size of the fan (that is, the fan diameter or blade size `tip to tip`) is limited by the height of the housing. Prior art housings therefore have had to have a sufficiently high vertical dimension to accommodate a fan of sufficient blade size, and thus to provide the necessary volume of cooling air without creating unacceptable noise and vibration levels.
The above-described prior art cooling system has several drawbacks. One is physical size, particularly the height, which requires the use of a sufficiently tall housing. Because ambient cooling air typically enters and/or exits the housing from the exposed sides, sufficient clearance must also be maintained around the housing to allow unimpeded air flow to the vent openings. This requirement can add 6" to 8" or more to the housing length and width, and thus to the amount of desk space required for the housing. The air inlet and exhaust vent openings on the front and sides of the housing, in addition to allowing cooling air in, also allow noise created by the fan and other internal components (such as disk drives) to be transmitted outside of the housing.
Various methods to increase the heat dissipation from heat generating components of computers or other electronic equipment are known in the prior art.
U.S. Pat. No. 4,702,154 issued to Dodson discloses the use of a fan mounted at an inclined angle.
U.S. Pat. No. 4,237,521 issued to Denker discloses the use of an internally mounted heat sink with diagonal fins to which heat generating electronic components such as transistors can be mounted.
U.S. Pat. No. 4,797,783 issued to Kohmoto et al discloses the use of multiple sets of fans.
U.S. Pat. No. 4,513,351 issued to Davis et al discloses the use of channels to distribute cooling air to heat generating computer components.
U.S. Pat. No. 4,520,425 issued to Ito and U.S. Pat. No. 4,644,443 issued to Swensen et al disclose the use of partitions and baffles to more effectively channel cooling air over heat generating electronic components.
Although structures such as those disclosed by the above patents may provide varying degrees of cooling, they add bulk, complexity, cost and inefficiency that has generally made their use less than optimal in desktop workstations.